1. Field of the Invention
The present invention relates to a transparent conductive laminated body, which is transparent in visible light region, having a conductive thin film on a film substrate. The transparent conductive laminated body of the present invention is used in usages of transparent electrodes for new display methods applied liquid crystal displays, and electroluminescence displays and touch panels etc. besides and antistatic and electromagnetic wave interception, etc. for transparent goods.
2. Description of the Prior Art
As a conventional transparent conductive thin film, a so-called conductive glass in which indium oxide thin film is formed on a glass plate is known well, but since a substrate is made of glass, the conductive glass is inferior in flexibility and workability, and it is not suitable for a certain usage. Therefore, in recent years, a transparent conductive thin film in which various kinds of plastic films including polyethylene terephthalate film is used as substrate are often used in the light of advantages, such as, a flexibility and workability etc. in addition to excellent shock resistance and lightweight.
However, transparent conductive thin films using the film substrate have a problem that transparency is decreased because of a large light reflection factor on surface thereof, and also have a problem that electric resistance is increased or disconnection of circuits may occur because of blemish given while in use since the conductive thin film is inferior in scratch-proof property. Especially in conductive thin films for touch panels, a pair of films facing countered to each other through a spacer are strongly contacted at depressed dots from the panel board side of one of the pair, and therefore it is required for the films to have excellent durable characteristics resisting a strong depressing impact, that is, dotting property. However, since an excellent dotting property was not realized in the transparent conductive thin films using the above described film substrate, the films had a problem that only a short life as a touch panel could be realized.
In Japanese Patent Application Laid-Open No. 6-222352,A, as a solution for the above described problem, a method of obtaining a transparent conductive laminated body is proposed in which a film with a specific film thickness is used as a film substrate, and onto one face of the film a thin film of dielectric substance with a light index of refraction smaller than a light index of refraction of the film substrate is formed, and further a transparent conductive thin film is sequentially formed thereon, and moreover onto the other face of the film substrate another transparent substrate is adhered through a transparent pressure sensitive adhesive layer. In this transparent conductive laminated body, while transparency and scratch-proof property of the conductive thin film are improved, dotting property as a material for touch panels is also improved. Since the transparent conductive laminated body concerned is used in many cases in a state being flexed in touch panels etc., improvement in flexibility is further desired.
An object of the present invention is to provide a transparent conductive laminated body in which a conductive thin film is prepared on a film substrate, such as a polyethylene terephthalate film, and a laminated body that has outstanding transparency, scratchproof property of a conductive thin film, and also excellent flexibility. Furthermore, an object of the present invention is to provide a touch panel with improved dotting property using the transparent conductive laminated body concerned.
As a result of wholehearted research of the present inventors, it was found that the above described object is attained using the transparent conductive laminated body shown below to perform the present invention.
Namely the present invention relates to a transparent conductive laminated body comprising a transparent dielectric substance thin film having two layers and furthermore a transparent conductive thin film being formed on one face of a transparent film substrate with thickness of 2 to 120 xcexcm, and a transparent substrate being adhered on another face of the film substrate through a transparent pressure sensitive adhesive layer, wherein a relationship of n3 less than n1 less than =n2 less than n4 is satisfied where a light index of refraction of the film substrate is defined as n1, a light indexes of refraction of the two layers of the dielectric substance thin films are defined as n2 and n3 from the film substrate side respectively, and a light index of refraction of the conductive thin film is defined as n4.
In the present invention, a dielectric substance thin film having a light index of refraction n3 smaller than a light index of refraction n1 of a film substrate is used between a film substrate and a conductive thin film, and on the other hand, a transparent substrate is prepared through a transparent pressure sensitive adhesive layer on another side of the film substrate to obtain an improved transparency of a transparent conductive laminated body and a scratch-proof property of the conductive thin film. Moreover the dielectric substance thin film has a structure containing two layers with a mutually different index of refraction, and optical properties may be improved and better flexibility as a dielectric substance thin film is also obtained as compared to a case where a thin film with an index of refraction smaller than an index of refraction of a film substrate is adopted, using a layer with an index of refraction n2 equal to an index of refraction n1 of a film substrate or greater than an index of refraction n1, and at the same time smaller than an index of refraction n4 of a conductive thin film as a layer in a side of the film substrate.
In the above described transparent conductive laminated body, it is preferable that the dielectric substance thin film with an index of refraction n2 is an organic substance or a mixture of an organic substance and an inorganic substance.
Moreover, in the above described transparent conductive laminated body, it is preferable that the dielectric substance thin film with an index of refraction n3 is an inorganic substance or of a mixture of an inorganic substance and an organic substance.
In the above described transparent conductive laminated body, a flexibility is improved, using an organic substance or a mixture of an organic substance and an inorganic substance as at least one layer of the two layers of dielectric substance thin films. Since an organic layer has better adhesion to film substrate, a dielectric substance thin film containing organic substance or a mixture of an organic substance and an inorganic substance may be preferably arranged on the substrate side.
Furthermore, the present invention relates to a touch panel in which a pair of panel boards with a conductive thin film is configured so that the conductive thin films face to each other through a spacer, wherein at least one panel board comprises the transparent conductive laminated body.
A durable property to inputting with pen (dotting property) of a touch panel using the above described transparent conductive laminated body may be improved, and at the same time flexibility may also be improved.